| Methods |
Prospective cohort study testing the performance of 1, 2, 3, 4 and 5 surgical masks worn in layers against the droplet filtration capacity of a N95 respirator. The study is described as cross‐over trial when all volunteers wore the combinations of layers, but this is not further described |
| Participants |
6 volunteers who wore the masks and had their droplet count taken |
| Interventions |
Pleated rectangular 3‐ply surgical mask |
| Outcomes |
Laboratory |
| Notes |
Risk of bias: high (report too brief to allow assessment)
Notes: the authors conclude that the best combination of 5 surgical masks scored a fit factor of 13.7, well below the minimum level of 100 required for a half face respirator. The reduction in particle count went from 2.7 for a singe mask to 5.5 for 5 masks worn at the same time. Multiple surgical masks filter ambient particles poorly. They should not be used as a substitute for N95 respirator unless there is no alternative. Cautiously the authors state that they cannot comment on the capacity of 5 layers of masks to stop infections such as SARS as the infective count of the SARS‐CoV is unknown
Fascinating small study with no details of assignment so it was classified as a cohort study. Unfortunately there is no indication of how comfortable 5 masks are to wear in a layer and no description of the volunteers |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Random sequence generation (selection bias) |
Unclear risk |
N/A |
| Allocation concealment (selection bias) |
Unclear risk |
N/A |
| Blinding (performance bias and detection bias)
All outcomes |
Unclear risk |
N/A |
| Incomplete outcome data (attrition bias)
All outcomes |
Unclear risk |
N/A |
| Selective reporting (reporting bias) |
Unclear risk |
N/A |
